Gentamicin distribution in tissues and pleural exudate. A comparison between bolus vs drip-infusion, microbiological assay vs enzyme multiplied immunoassay technique.

Concentrations of gentamicin in rat serum and tissues were compared after i.v. (30 mg/kg) bolus injection or continuous infusion. Serum and tissue specimens were collected after 0.5, 1 and 2 h and gentamicin assayed by the microbiological method; serum and pleural exudate samples were also evaluated by enzyme multiplied immunoassay technique (EMIT). Continuous infusion gave higher concentrations of antibiotic in serum after 0.5, 1 and 2 h; in pleural exudate, kidney and muscle after 1 and 2 h from the beginning of administration; the area under the concentration curve (0-2) for serum, pleural exudate and kidney were higher also. These data suggest that continuous infusion may attain the highest serum and tissue levels. Gentamicin concentrations in pleural exudate after both bolus and continuous infusion assayed by the microbiological method, were greater than EMIT. This difference may be explained by the synergistic action between the antibiotic and the pleural exudate.